Does KSP model buoyancy in air?

[Entropian]

Pretty much stated in the title.  Any ideas?

[Spricigo]

Since "Buoyancy" is just a result of gravity and pressure and KSP simulate those things i suspect it is. Question is: is the simulation god enough?

 

 

[Snark]

On 10/7/2020 at 6:21 PM, Entropian said:

Pretty much stated in the title.  Any ideas?

I don't actually know the answer, but I'd guess that the answer is almost certainly that no, it doesn't.  I'd be deeply astonished if the answer were otherwise.

[s_gamer101]

On 10/8/2020 at 12:29 PM, Spricigo said:

 

Since "Buoyancy" is just a result of gravity and pressure and KSP simulate those things i suspect it is. Question is: is the simulation god enough?

 

In real life, it is indeed resulting from gravity and pressure (which is resulting from gravity). But in KSP, there‘s most likely no buoyancy because in KSP‘s physical simulation, the atmospheric pressure isn‘t what it is in real life. For KSP, the pressure is probably just a number that is used to calculate the drag. So my conclusion is that there‘s no buoyancy.

[bewing]

I tested it, and the answer is almost certainly "no". I changed the mass of an empty RCS tank to .000001 kg in the cfg file. It would definitely float like a balloon at that mass, if buoyancy in air was modeled. Took all the fuel out, launched it into the air with a decoupler, and it fell right back down at 1G.

 

[Entropian]

I think it could be tested with a forcemeter (can't think of the right word) and a really light part.  I know about fluid dynamics, and my conclusion is that even if it was there, it would be negligible.  Maybe an ultralight airship would get the necessary displacement, but overall it would be relatively useless.  I'm going to get modding and see what I can do.

[A Fistful Of Double Downs]

I think it does since terminal velocity is affected by both air pressure and the density of your parts, and I've got a sneaking suspicion that "water" is just modeled in-game as a layer of atmosphere with a density of 1 ton per cubic meter, but I can't say I've ever tested it.

 

There are some airship mods out there that I haven't tried yet though, so you might get your answer by finding out how they model bouyancy.

[s_gamer101]

19 hours ago, A Fistful Of Double Downs said:

There are some airship mods out there that I haven't tried yet though, so you might get your answer by finding out how they model bouyancy.

They probably add some kind of „bouyancy“ for some of the parts they add.

19 hours ago, A Fistful Of Double Downs said:

and I've got a sneaking suspicion that "water" is just modeled in-game as a layer of atmosphere with a density of 1 ton per cubic meter, but I can't say I've ever tested it.

Why do you think so?

[Entropian]

2 hours ago, s_gamer101 said:

Why do you think so?

Air intakes work in water.

[s_gamer101]

7 hours ago, Entropian said:

Air intakes work in water.

That's a good point, maybe you and @A Fistful Of Double Downs are right and the water is simulated as some kind of a layer of the atmosphere, but there would be some more differences between it and the other layers of the atmosphere than just the density, like the visible water surface. And maybe the "water" is also the only layer of the atmosphere that does simulate buoyancy. The game might simulate buoyancy only when you are below the "water surface".

[bewing]

2 hours ago, s_gamer101 said:

but there would be some more differences between it and the other layers of the atmosphere than just the density, like the visible water surface. And maybe the "water" is also the only layer of the atmosphere that does simulate buoyancy. The game might simulate buoyancy only when you are below the "water surface".

I believe this is all correct. One other difference between the simulated air and water is viscosity.